Preparing to Add Borders

I am feeling a bit insecure about what I am about to do because I don't want to make a mistake. I sewed all of the star blocks into 4 strips and they each measure at 73.5" in length plus I have 4 corner blocks. My quilt top is currently 72" square and I want to add a narrow border between the two. Somehow I need to make it all fit properly. :)

My plan is to trim the top to 70.5" square and then add the narrow blue border to make up the difference in size. I am cutting the blue strips at 2" and they will finish at 1.5". That should add up to - hopefully the right size, grrrrrrrr, my brain is a jumble so I hope I got it right.

I am off to start trimming my quilt top ****nerve-wracking**** and then cut and add my narrow blue borders. If all goes well, fingers crossed, I plan to add the star border as well. :)